Manufacture of ethyl chloride from petroleum refinery gas



Jan. 23,1934. s. a HJERPE r AL 1, ,8

mumcwugaor EfII IYL cfiLonInE' FROM PETROLEUM nnvmsnzwgs Y .Eiled April 8, 1932 M wmzz Patented Jan. 23, 1934 UNITED STATES PATENT OFFICE MANUFACTURE OF ETHYL CHLORIDE FROM 1 PETROLEUM REFINERY GAS Texas Application April 8, 1932. Serial No. 604,076

8 Claims. (Cl- 260-166) This invention relates to manufacture of ethyl chloride from petroleum refinery gas; and more specifically it comprises a process wherein tail gas from the customary condensers of cracking stills and coke stills is first stripped of pentanes and higher boiling constituents by means of ordinarily compression and/or absorption methods; is then fractionated to isolate a mixture of ethylene and lower boiling constituents; the isolated 10 mixture is contacted with hydrogen chloride in the presence of a chlorination catalyst, such as aluminum chloride, to form ethyl chloride; the ethyl chloride is stripped from accompanying diluent gases by being scrubbed with and absorbed in a petroleum absorbent oil; and finally the ethyl chloride is recovered by distillation from the absorbent oil; all as more fully hereinafter set'forth and as claimed.

In the present invention petroleum refinery gas is utilized in the-manufacture of ethyl chloride and the ethyl chloride is recovered from the disproportionately large quantity of diluent gas in which it exists when so manufactured.

Another object of our invention is, in the aforesaid utilization of petroleum refinery gas, to produce ethyl chloride which will be substantially free of other chlorides such as propyl chloride.

By the invention described herein we attain the above objects in remarkable degree.

The operation of cracking stills and coking stills in refinery operations entails the production of a large quantity of material boiling below the gasoline fraction. For practical reasons such stills are commonly provided with individual condensers whichdo not condense the major portion of such lower boiling material. Good refinery design ordinarily provides compression and absorption plant facilities for liquefying a portion of this gas into what the industry commonly denominates natural gasoline, but after the recovery of this natural gasoline there is a great amount of gaseous residue which is commonly known as stripped refinery gas or dry refinery gas. This stripped gas is the raw material of the process which we have invented and which we claim herein.

The above described stripped refinery gas, when intendedas raw material for the process of this invention, may have been stripped not only of pentane and higher boiling constituents, but also of butane and butylene. The presence or absence of butane and'butylene in the stripped gas is not particularly important except as it affects the pressure and temperature necessary to attain the self-cooling prior to fractionation, as later described.

The accompanying drawing, Fig. 1, is a schematic representation, of certain apparatus elements useful in conducting our process, the flow of materials therethrough being indicated by lines and arrows. Our invention will be described in conjunction with this drawing. Stripped refinery gas, received through line 1 is compressed by compressor 2, then cooled by water in a cooler 3, and then fractionated in fractionator 4. The gas received through line 1 is ordinarily at atmospheric temperature and it will frequently be as warm as 100 F. when it leaves the cooler 3. We ordinarily operate the fractionator 4 at a pressure of about 50 pounds above atmospheric and we there .take off an overhead cut containing ethylene and all lower boiling gases such as methane, air, and hydrogen. This cut may, of course, contain some ethane and tracesof higher boiling constituents.

Ethane, and higher boiling constituents such as propane, propylene, butane, etc., are taken from the bottom of the fractionator as liquid. When operating on a gas having an analysis such as that hereinafter set out we are able to effect a 30 good separation of ethylene and lower boiling constituents from ethane and higher boiling constituents by maintaining a top temperature in fractionator 4 very slightly warmer than minus 100" C. The proper top temperature for gas of any other analysis can readily be obtained with the aid of widely published tables of physical constants and well known laws of physical chemistry. The low temperature in the fractionator is attained by self cooling of the gases resulting from on expansion through an expansion valve 5 just prior to their entry into fractionator 4. The pressure generated by the compressor 2 is whatever pressure is necessary to attain the desired refrigeration. The gas may be permitted to expand 95 through a working engine instead of a reducing valve 5 and a lower initial pressure will then attain the same refrigeration effect. Onegas with which we have operated our process had the following composition:

Per cent Methane 45 Ethylene 5 Ethane 20 Propane-propylene 23 Butane and heavier '7 With such a gas we found it necessary to maintain a pressure in the neighborhood of five hundred pounds above atmospheric beyond compressor 2 in order to maintain a pressure of fifty pounds in fractionator 4 and a top temperature sents an alternative form of fractionator 4, and this 'form of fractionator diil'ers from that of Fig. 1 only in that the gas, after expansion at reducing valve 5, is passed through a cooling coil 6' in the head of the fractionator before open introduction into the fractionator.

The ethylene content of the stripped refinery gas, in mixture with methane and other lower boiling constituents, leaves the fractionator 4 through line 7 and this material is now mixed with hydrogen chloride, the entire mixture of hydrogen chloride, ethylene, methane, etc. is then brought'to the desired temperature and introduced into the presence of a .catalyst, resulting in the prompt generation of ethyl chloride. Anhydrous aluminum chloride is an effective catalyst for this purpose, and bismuth chloride and other chlorination catalysts have been found satisfactory. We find that our process can be practically and profitably conducted with gaseous mixtures in which the ethylene content of the fractionator efiiuent is even less than 10 per cent although we prefer not to operate on gases much poorer in ethylene than 10 per cent. The gas analysis already recorded is typical and it will be noted that the ethylene content of the methaneethylene fraction is only ten per cent. This extreme dilution of the ethylene is one of the two factors which give rise to our problem for it results in an extremely dilute ethyl chloride which must then be recovered.

Referring to the drawing again, a source of hydrogen chloride is shown at 8 and a blower 9 is shown for transferring it therefrom to the gas line 7. When such a blower is used we reduce the pressure on the gas in line 7 by a valve just before its junction with the hydrogen chloride line. We find that with equal advantage we can omit the blower 9 when the hydrogen chloride source 8 is not too far removed and induce the flow of hydrogen chloride by connecting it to an injector.in-'

serted in line 7 at the junction of the two. In either case wereduce the pressure 01' the gases in line 7 so that the pressure in the catalyst chamber is approximately atmospheric. Hydrogen chloride is used in the proportion of 36.5 parts (or very slightly less) by weight to 28 parts of ethylene. This corresponds to one volume (or very slightly less) of hydrogen chloride toone volume of ethylene.

The conjoint stream of hydrogen ,chloride, ethylene, methane, etc. is first passed through a tubular coil 10 in a heater 11 and brought to a temperature of about 350 F. and it is then brought into the presence of catalyst in chamber 12 which is surrounded by a temperature maintaining device 13. A contact of from one to two minutes with the catalyst is ordinarily ample when using reasonably fresh catalyst. A temperature of 350 F. should not be exceeded when using very fresh aluminum chloride as catalyst, because of its tendency to sublime, but as it gradually becomes exhausted we find that it is possible to use temperatures approaching 400" F. After one or two minutes the ethylene will have been converted to ethyl chloride and will exist as a vapor, in very dilute form, in mixture with the methane, etc. are next cooled by means of a cooler 14 and if HCl has been used in such quantity as to result in free HCl beyond the catalyst chamber 12 it is next removed in appropriate manner.

We have found that petroleum oils are good absorbents of ethyl chloride but have no sub-' stantial absorbent action toward the accompanying products of our reaction, and we have solved the difficult problem of recovering the ethyl chloride by the use of an absorption sys- .90

tem wherein the gases are scrubbed with,, and the ethyl chloride is absorbed in, a petroleumabsorbent oil which has no substantial volatility in relation to that of ethyl chloride; the absorbent oil after scrubbing the gases and absorbing the ethyl chloride is sent to a stripping still and fractionator' for removal of the ethyl chloride I content; and finally the undiluted vapors of ethyl chloride may be separately condensed, if desired in liquid form. lustrated an absorption tower 16 and we ordinarily operate this under a pressure of about fifty pounds above atmospheric, this pressure being secured by the aid of a compressor 15. The

ethyl chloride vapors and accompanying gas are 108 introduced into the bottom of the absorption tower, as shown, and absorbent oil is fed down from the top, as shown, in countercurrent flow to the material being scrubbed. A series of plates in the absorber adds tremendouslyto its effectiveness. After having had its ethyl chloride content removed, the tail gas is discharged from the top of absorption tower 16 through line 17 and out of the system, to be used for, other purposes. Absorbent oil containing ethyl chloride is removed from the base of absorption tower 16 through line 18 and conveyed to the combined stripping still and fractionator 19 wherein it is heated by circulation of a hot fluid through a closed coil 20 and the ethyl chloride content is distilled out. The ethyl chloride vapors pass from the top of tower 19 through line 21 to condenser 22, and ethyl chloride is saparately discharged therefrom through line 23. The pressure generated in absorption tower 16 by means of compressor 15 is advantageously continued through to condenser 22 so that the ethyl chloride can be condensed withthe aid of water at commonly obtainable temperature. A circulating pump withdraws stripped absorbent oil from the base of stripping still 19, through line 24, and discharges it through line 25 back into the top of the absorption tower 16.

When we use the expression relatively nonvolatile petroleum absorbent oil we mean a petroleum absorbent oil which has no substantial vapor pressure at the temperature necessary for the distillation of ethyl chloride therefrom.

The low temperature gases leaving fract onator 4 through line 7 can advantageously be utilized to cool the gases prior to their entry into absorber 16, or to condense the ethyl chloride vapors from stripping tower '19, or may be divided between these two uses. heat is, of course, accomplished by separately passing two streams through heat interchange equipment of common type, and passage therethrough in counter-direction will have the usual advantage of more complete heat interchange. 150

The vapors and gases 80 In the drawing we have il- 100 Such interchange of Our invention is a distinct advance over the prior art in that:

1. It permits manufacture of technically pure ethyl chloride from the complex gases which constitute a by-product of petroleum refineries.

2. It provides a cheap, eflicient and practical means whereby it is possible to capture and isolate the ethyl chloride from the large mass of accompanying gas in which it is diluted many fold.

3. By an early removal of propane, propylene, etc. we are enabled to manufacture ethyl chloride substantially free of propyl chloride, isopropyl chloride, etc., from petroleum refinery gas.

4. It obviates the necessity and expense in manufacture of ethyl chloride from refinery gas of separating ethylene from methane by liquefaction and distillation.

What we claim is:

1. The process of manufacturing ethyl chloride from petroleum refinery gas which comprises fractionating ethylene and lower boiling constituents from ethane and higher boiling constituents; contacting the lower boiling fraction in the presence of a chlorination catalyst, with hydrogen chloride-in combining proportions to convert the ethylene content into ethyl chloride;

v a group consisting of aluminum chloride and bismuth chloride, 1 I

3. The processof'claim 1 wherein the chlorination catalyst is aluminum chloride.

4.'The' process of manufacturing ethyl chloride from petroleum refinery gas which comprises'fractionating' petroleumrefinery gas to separate a fraction containingethylene as the Y highest boiling constituentycontacting this gas in' thepresence of a chlorination catalyst with hyd rog enchloride-to convert the ethylene content int'o ethylchloride; scrubbing the resultant mixture with a relatively non volatile petroleum absorbent oil to absorb. ethyl chloride; removing the absorbent oil and distilling the ethyl chloride out, thereby separately obtaining the ethyl chloride.

5. The process of manufacturing ethyl chloride from petroleum refinery gas which comprises fractionating petroleum refinery gas to separate a fraction containing ethylene as the highest boiling constituent; introducing hydrogen chloride into this fraction in proportion of approximately, but not greater than, 36.5 parts by weight to each 28 parts by weight of ethylene content of the gas fraction; introducing this mixture into the presence of a chlorination catalyst, to convert the ethylene into ethyl chloride, after first heating the mixture to a temperature slightly below the volatilization temperature of the catalyst; cooling the resultant products to ordinary atmospheric temperatures; scrubbing the gases with a relatively non-volatile petroleum absorbent oil to absorb the ethyl chloride; removing the absorbent oil and distilling the ethyl chloride therefrom.

6. The process of claim 5 wherein the chlorination catalyst is a metallic chloride selected from a group consisting of aluminum chloride and bismuth chloride.

7. The process of claim 5 wherein the chlorination catalyst is aluminum chloride.

8. In the manufactureof ethyl chloride from petroleum refinery gas wherein the refinery gas is fractionated at low temperatures, and a so fractionated portion is caused to react with hydrogen chloride at a temperature substantially above ordinary atmospheric temperatures to I form ethyl chloride, and the ethyl chloride is then absorbed from its accompanying constituents by. an absorbent oil, the process which comprises separately passing the low temperature products of the fractionation and the higher temperature products of the reaction, in counter direction, in heat transfer relation with one an- 

